A confocal microscope and a total-internal-reflection fluorescence microscope are widely used for observing living cells, and commonly use a laser light source. There has been proposed a microscope that can be commonly used for a confocal microscope and a total-internal-reflection fluorescence microscope (see, for example, Japanese Patent Application Laid-Open No. 2005-121796).
However, in the conventional microscope, upon changing a confocal microscope to a total-internal-reflection fluorescence microscope, an optical member for converging laser light to a total-internal-reflection condition area on a pupil position of an objective lens has to be inserted to an illumination optical system. Accordingly, a large exchanging mechanism is necessary, so that the microscope becomes large and expensive.